Jog Structures at Both Ends of the Tepetarla Segment Ruptured as the First Subevent of the 1999 Izmit Earthquakes, Turkey, Revealed by Acoustic Surveys in the Izmit Bay and the Sapanca Lake
Abstract
Size and geometry of jogs among fault segments play important roles in rupture propagation during large earthquakes. We carried out a very detail acoustic survey around the both ends of the Tepetarla (Sapanca) segment, which ruptured as the first sub-event of the 1999 Izmit earthquakes of Mw7.4, in the Izmit Bay and the Sapanca Lake, using a very high-resolution, acoustic profiling system ?Sono-prob?(SP-3W; 3-8kH) and a sidescan sonar (DF1000). Survey lines were designed at 250 m interval to capture the details of fault geometry. The Tepetarla segment on land is traceable for 19km almost straightly and continuously trending east to west with an average displacement of 2.8+-0.2 (one sigma) m. East of the segment continues in to the Sapanca Lake for about10km and makes a releasing double bends as the jog structure between Tepetarla and Arifiye segments. The double bends is 8 km-long and 2 km-wide consists of en-echelon faults with normal component of slip. East on the lake, the jog appeared on land for 2 km-long, as a 500 m-wide graben. Although South on the Arifiye segment there are several secondary faults making a hose tail structure, we couldn?t find any recent fault south of the tepetarla segment in the Sapanca Lake. West of the tepetarla segment continues into the Izmit Bay for 6 km making a releasing pull-apart structure between Golcuk and Tepetarla segments. The basin is 8 km-long, 3 km-wide and about 15 square km, surrounded by faults that have normal component. Subsidence of the large area of south coast of the Izmit Bay during the earthquake suggests that this pull-apart structure stretches at least several km deep. Those differentiations of geometry and size of jogs might strongly influence the rupture process of the 1999 Izmit earthquake.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.S11B1157A
- Keywords:
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- 3000 MARINE GEOLOGY AND GEOPHYSICS;
- 7205 Continental crust (1242);
- 7221 Paleoseismology;
- 7223 Seismic hazard assessment and prediction